A kinetic study of bread staling by differential scanning calorimetry. The effect of loaf specific volume

Abstract

Changes in the starch fraction of bread at 21°C have been measured as a function of loaf specific volume using differential scanning calorimetry (DSC). Data from five bakes were fitted by Avrami equations 4 = exp ( A n ) (where 4 is the fraction of the total thermal change still to occur) using an iterative non-linear least squares procedure which enabled simultaneous estimation of limiting value, rate constant ( k ) and Avrami exponent (n). The method allowed the fit of a number of different models to be tested. It was concluded that Avrami exponents from each bake were the same and < 1 and that the rate constants were also equal. For comparison, crumb cornpressibility measurements were made on the same loaves used for DSC. These data were also analysed in a similar way. An adequate fit in this case was given by an Avrami exponent of 1 ; however, rate constants appeared to vary with loaf specific volume.

NIR measurements of the development of crystallinity in stored bread crumb

“…II) was found to be consistent with, although at the upper end of, the range of published data [2,7].…”

“…E x p e rimental data from the DSC and NIR measure m e n t s were analysed separately by fitting an Avrami equation to each data set and comparing the fits statistically [2,7].…”

Effect of tea polyphenols on the retrogradation of rice starch

“…The enthalpy values of the retrograded starch reflect the melting of the crystallites formed by the association between adjacent double helices during gel storage (Hoover & Senanayake, 1996), and this endotherm peak was due to the melting of retrograded amylopectin (Abd, Norziah, & Seow, 2000;Fearn & Russell, 1982) rather than amylose. Table 2 lists the changes in retrogradation enthalpy and retrogradation ratio (DH r /DH g ) of gelatinized RS with difference concentrations of TPLs as a function of storage time.…”

Effect of various dextrin substitutions for wheat flour on dough properties and bread qualities

“…Then recrystallization of amylopectin gradually occurs, followed by gathering of branched chain molecules (Hizukuri, 2000). Fearn and Russell (1982) applied DSC to measure the structural changes of starch in bread during aging. They observed that when staled bread was heated in the DSC, a prominent endotherm peak was present around 50°C, which was absent in the fresh bread, and notably increased with storage time.…”